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Title: Metallicity of Ca 2Cu 6P 5 with single and double copper-pnictide layers

We report thermodynamic and transport properties, and also theoretical calculations, for Cu-based compound Ca 2Cu 6P 5 and compare with CaCu 2-δP 2. Both materials have layers of edge-sharing copper pnictide tetrahedral CuP 4, similar to Fe–As and Fe–Se layers (with FeAs 4, FeSe 4) in the iron-based superconductors. Despite the presence of this similar transition-metal pnictide layer, we find that both Ca 2Cu 6P 5 and CaCu 2-δP 2 have temperature-independent magnetic susceptibility and show metallic behavior with no evidence of either magnetic ordering or superconductivity down to 1.8 K CaCu 2-δP 2 is slightly off-stoichiometric, with δ = 0.14. Theoretical calculations suggest that unlike Fe 3d-based magnetic materials with a large density of states (DOS) at the Fermi surface, Cu have comparatively low DOS, with the majority of the 3d spectral weight located well below Fermi level. The room-temperature resistivity value of Ca 2Cu 6P 5 is only 9 μΩ-cm, due to a substantial plasma frequency and an inferred electron-phonon coupling λ of 0.073 (significantly smaller than that of metallic Cu). Also, microscopy result shows that Cu–Cu distance along the c-axis within the double layers can be very short (2.5 Å), even shorter than metallic elemental copper bondmore » (2.56 Å). The value of dρ/dT for CaCu 2-δP 2 at 300 K is approximately three times larger than in Ca 2Cu 6P 5, which suggests the likelihood of stronger electron-phonon coupling. Lastly, this study shows that the details of Cu–P layers and bonding are important for their transport characteristics. In addition, it emphasizes the remarkable character of the DOS of ‘122’ iron-based materials, despite much structural similarities.« less
ORCiD logo [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Alabama at Birmingham, Birmingham, AL (United States)
Publication Date:
Grant/Contract Number:
NA0002014; AC05-00OR22725
Accepted Manuscript
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 671; Journal Issue: C; Journal ID: ISSN 0925-8388
Research Org:
Univ. of Alabama at Birmingham, Birmingham, AL (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC)
Country of Publication:
United States
36 MATERIALS SCIENCE; copper pnictide; thermal conductivity; superconductivity; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1251195; OSTI ID: 1342596